Write a function that returns triangular part of matrix using loops

Question

Jerry 2013-9-26

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编辑： Friday N. Abolorunke 2020-6-8

I just started to learn how to program using matlab and in class we have covered if and for loops but I am really not sure how to solve this problem. Can someone please help?

Write a function that inputs a square matrix and returns
another matrix which is identical to the first, except that the elements below the diagonal are
set to zero. 
Your function should use nested for loops. If given a matrix:
4 3 4 4
4 1 4 2
1 2 1 4
4 3 4 1
It should return the following matrix:
4 3 4 4
0 1 4 2
0 0 1 4
0 0 0 1
Show your output for an illustrative 5x5 matrix input.

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Jan 2013-9-26

编辑：Jan 2013-9-26

Because this is a homework, it is your turn to show us, what you have tried so far and explain which problems occur. Tip: You can solve it by two FOR loops and compare the indices.

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Answer 1

Matt J 2013-9-26

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编辑：Matt J 2013-9-26

在 MATLAB Online 中打开

Probably not what you're looking for, but course instructors are so dumb sometimes...

 function B=uppertri(A)
   for i=1
    for j=1
      B=triu(A);
    end
   end

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Answer 2

Friday N. Abolorunke 2020-6-8

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编辑：Friday N. Abolorunke 2020-6-8

在 MATLAB Online 中打开

function summa = halfsum(A)
[m,n] = size(A);
for ii = 1:m
    for jj = 1:n
        if ii > jj 
            A(ii,jj) = 0
            summa = sum(A(:));
        elseif ii == 1
            summa = sum(A);
        end  
    end
end
end
        

For a 3 x 3 matrix. you'll want to assign zero to A(2,1),A(3,1) and A(3,2). Notice that the index of the elements in the row most always be greater than that of the col